CVE-2025-39766

CVE Details

Release Date:	2025-09-11
Impact:	Moderate	What is this?

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: Make cake_enqueue return NET_XMIT_CN when past buffer_limit The following setup can trigger a WARNING in htb_activate due to the condition: !cl->leaf.q->q.qlen tc qdisc del dev lo root tc qdisc add dev lo root handle 1: htb default 1 tc class add dev lo parent 1: classid 1:1 \ htb rate 64bit tc qdisc add dev lo parent 1:1 handle f: \ cake memlimit 1b ping -I lo -f -c1 -s64 -W0.001 127.0.0.1 This is because the low memlimit leads to a low buffer_limit, which causes packet dropping. However, cake_enqueue still returns NET_XMIT_SUCCESS, causing htb_enqueue to call htb_activate with an empty child qdisc. We should return NET_XMIT_CN when packets are dropped from the same tin and flow. I do not believe return value of NET_XMIT_CN is necessary for packet drops in the case of ack filtering, as that is meant to optimize performance, not to signal congestion.

See more information about CVE-2025-39766 from MITRE CVE dictionary and NIST NVD

NOTE: The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 metrics

Base Score:	6.8
Vector String:	CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Version:	3.1
Attack Vector:	Local
Attack Complexity:	Low
Privileges Required:	None
User Interaction:	None
Scope:	Unchanged
Confidentiality Impact:	None
Integrity Impact:	Low
Availability Impact:	High

Errata information

Platform	Errata	Release Date
Oracle Linux version 10 (kernel-uek)	ELSA-2025-25754	2025-11-09
Oracle Linux version 7 (kernel-uek)	ELSA-2025-20663	2025-10-11
Oracle Linux version 8 (kernel-uek)	ELSA-2025-20663	2025-10-11
Oracle Linux version 8 (kernel-uek)	ELSA-2025-25757	2025-11-10
Oracle Linux version 9 (kernel-uek)	ELSA-2025-25754	2025-11-09
Oracle Linux version 9 (kernel-uek)	ELSA-2025-25757	2025-11-10